This invention relates to an automatic telephone answering apparatus.
In a conventional automatic telephone answering apparatus, a predetermined outgoing message is sent out upon reception of an incoming call to invite a caller to leave a note (i.e., a message), and the caller's message is recorded on an incoming message tape.
However, conventional automatic telephone answering apparatus do not provide multiple functions and a simple construction. Demand has arisen for a simple multifunction automatic telephone answering apparatus, which responds to every need of the user.
In a conventional automatic telephone answering apparatus, a subscriber can call his telephone number in the same manner as a third calling party to access a group of messages recorded on an incoming message tape by means of a remote control unit coupled to a telephone set or directly to a telephone line.
In order to perform such remote control, a specific remote control code is sent to the apparatus to cause the apparatus to respond to the specific code.
For this purpose, in the conventional system a security code is used as the remote control signal. According to this system, the security code as the remote control signal is generated in response to a DTMF (dual tone multifrequency) signal in a pushbutton telephone. In principle, a simple remote control unit having the same function as described above can be used as one remote control system of the present invention.
In such a simple remote control unit, a 2-bit code is adopted when the number of different functions to be operated in response to the control code is small. (This unit is basic and is used only by an ordinary subscriber, and does not, therefore, require a security code).
In this type of remote control unit, the automatic telephone answering apparatus receives the remote control signal during an OGM (outgoing message/specific message for a caller) transmission, as well as the DTMF signal. The remote control signal is sent through the telephone line and is in the voice frequency band. When the OGM has a frequency component very similar to that of the remote control signal, an operation failure occurs.
The remote control unit of the automatic telephone answering apparatus must guarantee security (secrecy) for a third party. At the same time, when a DTMF signal is used as a security code and a remote control signal, and when a simple system having the same function as that of the above remote control unit is used, failure must be eliminated and remote control must be made reliable.